#include "utils/logger.h"
#include "render/gl_shared.h"
#include "render/render_shared.h"
#include "render/render.h"

HDC hDC = NULL;
HGLRC hRC = NULL;

const char *GL_ErrorString( int err )
{
	switch( err )
	{
	case GL_STACK_OVERFLOW:
		return "GL_STACK_OVERFLOW";
	case GL_STACK_UNDERFLOW:
		return "GL_STACK_UNDERFLOW";
	case GL_INVALID_ENUM:
		return "GL_INVALID_ENUM";
	case GL_INVALID_VALUE:
		return "GL_INVALID_VALUE";
	case GL_INVALID_OPERATION:
		return "GL_INVALID_OPERATION";
	case GL_OUT_OF_MEMORY:
		return "GL_OUT_OF_MEMORY";
	default:
		return "UNKNOWN ERROR";
	}
}

void GL_CheckError()
{
	GLenum err;
	if ( (err = glGetError()) != GL_NO_ERROR )
		LogMsg( "OpenGL Error: %s", GL_ErrorString( err ) );// Msg("OpenGL Error: %s [%s]\n", GL_ErrorString(err), GL_TargetToString(tex->target));
}

void GL_CheckErrorEx( const char* filename, int line )
{
	GLenum err;
	if ( (err = glGetError()) != GL_NO_ERROR )
		LogMsg( "OpenGL Error: %s at %s:%i", GL_ErrorString( err ), filename, line );// Msg("OpenGL Error: %s [%s]\n", GL_ErrorString(err), GL_TargetToString(tex->target));
}

void GL_CheckErrorFunction(const char* expression, const char* filename, int line)
{
	GLenum err;
	if ( (err = glGetError()) != GL_NO_ERROR )
		LogMsg( "OpenGL Error: %s (%s) at %s:%i", expression, GL_ErrorString( err ), filename, line );// Msg("OpenGL Error: %s [%s]\n", GL_ErrorString(err), GL_TargetToString(tex->target));
}

void GL_SetTexture( int slot, uint texture )
{
}

uint GetGLBlendFactor(BlendFactor factor)
{
	switch (factor)
	{
	case BF_ZERO:
		return GL_ZERO;
	case BF_ONE:
		return GL_ONE;
	case BF_SRC_COLOR:
		return GL_SRC_COLOR;
	case BF_ONE_MINUS_SRC_COLOR:
		return GL_ONE_MINUS_SRC_COLOR;
	case BF_DST_COLOR:
		return GL_DST_COLOR;
	case BF_ONE_MINUS_DST_COLOR:
		return GL_ONE_MINUS_DST_COLOR;
	case BF_SRC_ALPHA:
		return GL_SRC_ALPHA;
	case BF_ONE_MINUS_SRC_ALPHA:
		return GL_ONE_MINUS_SRC_ALPHA;
	case BF_DST_ALPHA:
		return GL_DST_ALPHA;
	case BF_ONE_MINUS_DST_ALPHA:
		return GL_ONE_MINUS_DST_ALPHA;
	case BF_CONSTANT_COLOR:
		return GL_CONSTANT_COLOR;
	case BF_ONE_MINUS_CONSTANT_COLOR:
		return GL_ONE_MINUS_CONSTANT_COLOR;
	case BF_CONSTANT_ALPHA:
		return GL_CONSTANT_ALPHA;
	case BF_ONE_MINUS_CONSTANT_ALPHA:
		return GL_ONE_MINUS_CONSTANT_ALPHA;
	default:
		break;
	}

	return 0;
}

GLint GetGlWrap(TextureWrap wrap)
{
	GLint param = 0;

	if (wrap == TW_REPEAT)
		param = GL_REPEAT;
	else if (wrap == TW_MIRRORED_REPEAT)
		param = GL_MIRRORED_REPEAT;
	else if (wrap == TW_CLAMP_TO_EDGE)
		param = GL_CLAMP_TO_EDGE;
	else if (wrap == TW_CLAMP_TO_BORDER)
		param = GL_CLAMP_TO_BORDER;

	return param;
}

GLint GetGlTexFilter(TextureFilter filter)
{
	GLint param = 0;

	if (filter == TF_LINEAR)
		param = GL_LINEAR;
	else if (filter == TF_NEAREST)
		param = GL_NEAREST;
	else if (filter == TF_LINEAR_MIPMAP_LINEAR)
		param = GL_LINEAR_MIPMAP_LINEAR;
	else if (filter == TF_LINEAR_MIPMAP_NEAREST)
		param = GL_LINEAR_MIPMAP_NEAREST;
	else if (filter == TF_NEAREST_MIPMAP_LINEAR)
		param = GL_NEAREST_MIPMAP_LINEAR;
	else if (filter == TF_NEAREST_MIPMAP_NEAREST)
		param = GL_NEAREST_MIPMAP_NEAREST;

	return param;
}

uint GetGLPF(PixelFormat pf)
{
	return 0;
	//return uint32_t();
}

// Kirill: Remove to render_main.cpp or something else
uint GetGLInternalPF(PixelFormat pf)
{
	switch (pf)
	{
	case PF_UNKNOWN:
		return 0;

	case PF_R8G8B8:
	case PF_R8G8B8F:
		return GL_RGB;

	case PF_R8G8B8A8:
	case PF_R8G8B8A8F:
		return GL_RGBA;
	}

	return 0;
}

uint GetGLTypePF(PixelFormat pf)
{
	switch (pf)
	{
	case PF_UNKNOWN:
		return 0;

	case PF_R8G8B8:
	case PF_R8G8B8A8:
		return GL_UNSIGNED_BYTE;

	case PF_R8G8B8F:
	case PF_R8G8B8A8F:
		return GL_FLOAT;
	}

	return 0;
}

#define LOAD_GL_FUNC(functype, funcname) \
{ \
	funcname = (functype)wglGetProcAddress(#funcname); \
	if (funcname == NULL) \
		LogMsg("Failed to load %s", #funcname); \
}

bool GL_CheckExtensions(const char* name)
{
	const char* extensions = (const char*)glGetString(GL_EXTENSIONS);
	if (strstr(extensions, name)) {
		LogMsg("Found: %s", name);
		return true;
	}
	
	LogMsg("Not found: %s", name);
	return false;
}

void GL_CreateContext()
{
	// create opengl context
	PIXELFORMATDESCRIPTOR pfd;
	int iFormat;

	HWND hWnd = (HWND)R_GetWindow();

	/* get the device context (DC) */
	hDC = GetDC(hWnd);

	/* set the pixel format for the DC */
	ZeroMemory(&pfd, sizeof(pfd));
	pfd.nSize = sizeof(pfd);
	pfd.nVersion = 1;
	pfd.dwFlags = PFD_DRAW_TO_WINDOW | PFD_SUPPORT_OPENGL | PFD_DOUBLEBUFFER;
	pfd.iPixelType = PFD_TYPE_RGBA;
	pfd.cColorBits = 24;
	pfd.cDepthBits = 16;
	pfd.iLayerType = PFD_MAIN_PLANE;
	iFormat = ChoosePixelFormat(hDC, &pfd);
	SetPixelFormat(hDC, iFormat, &pfd);

	LogMsg("SetPixelFormat successful");

	/* create and enable the render context (RC) */
	hRC = wglCreateContext(hDC);
	LogMsg("wglCreateContext successful");

	wglMakeCurrent(hDC, hRC);
}

void GL_Load()
{
	GL_CreateContext();

	const char* vendor_string = (const char*)glGetString(GL_VENDOR);
	const char* renderer_string = (const char*)glGetString(GL_RENDERER);
	const char* version_string = (const char*)glGetString(GL_VERSION);
	const char* extensions_string = (const char*)glGetString(GL_EXTENSIONS);

	LogMsg("GL_VENDOR: %s", vendor_string);
	LogMsg("GL_RENDERER: %s", renderer_string);
	LogMsg("GL_VERSION: %s", version_string);
	LogMsg("GL_EXTENSIONS: %s", extensions_string);

	// OpenGL 1.3
	LOAD_GL_FUNC( PFNGLACTIVETEXTUREPROC,   glActiveTexture);
	LOAD_GL_FUNC( PFNGLSAMPLECOVERAGEPROC,  glSampleCoverage);
	LOAD_GL_FUNC( PFNGLCOMPRESSEDTEXIMAGE3DPROC, glCompressedTexImage3D);
	LOAD_GL_FUNC( PFNGLCOMPRESSEDTEXIMAGE2DPROC, glCompressedTexImage2D);
	LOAD_GL_FUNC( PFNGLCOMPRESSEDTEXIMAGE1DPROC, glCompressedTexImage1D);
	LOAD_GL_FUNC( PFNGLCOMPRESSEDTEXSUBIMAGE3DPROC, glCompressedTexSubImage3D);
	LOAD_GL_FUNC( PFNGLCOMPRESSEDTEXSUBIMAGE2DPROC, glCompressedTexSubImage2D);
	LOAD_GL_FUNC( PFNGLCOMPRESSEDTEXSUBIMAGE1DPROC, glCompressedTexSubImage1D);
	LOAD_GL_FUNC( PFNGLGETCOMPRESSEDTEXIMAGEPROC, glGetCompressedTexImage);
	LOAD_GL_FUNC( PFNGLCLIENTACTIVETEXTUREPROC, glClientActiveTexture);
	LOAD_GL_FUNC( PFNGLMULTITEXCOORD1DPROC, glMultiTexCoord1d);
	LOAD_GL_FUNC( PFNGLMULTITEXCOORD1DVPROC, glMultiTexCoord1dv);
	LOAD_GL_FUNC( PFNGLMULTITEXCOORD1FPROC, glMultiTexCoord1f);
	LOAD_GL_FUNC( PFNGLMULTITEXCOORD1FVPROC, glMultiTexCoord1fv);
	LOAD_GL_FUNC( PFNGLMULTITEXCOORD1IPROC, glMultiTexCoord1i);
	LOAD_GL_FUNC( PFNGLMULTITEXCOORD1IVPROC, glMultiTexCoord1iv);
	LOAD_GL_FUNC( PFNGLMULTITEXCOORD1SPROC, glMultiTexCoord1s);
	LOAD_GL_FUNC( PFNGLMULTITEXCOORD1SVPROC, glMultiTexCoord1sv);
	LOAD_GL_FUNC( PFNGLMULTITEXCOORD2DPROC, glMultiTexCoord2d);
	LOAD_GL_FUNC( PFNGLMULTITEXCOORD2DVPROC, glMultiTexCoord2dv);
	LOAD_GL_FUNC( PFNGLMULTITEXCOORD2FPROC, glMultiTexCoord2f);
	LOAD_GL_FUNC( PFNGLMULTITEXCOORD2FVPROC, glMultiTexCoord2fv);
	LOAD_GL_FUNC( PFNGLMULTITEXCOORD2IPROC, glMultiTexCoord2i);
	LOAD_GL_FUNC( PFNGLMULTITEXCOORD2IVPROC, glMultiTexCoord2iv);
	LOAD_GL_FUNC( PFNGLMULTITEXCOORD2SPROC, glMultiTexCoord2s);
	LOAD_GL_FUNC( PFNGLMULTITEXCOORD2SVPROC, glMultiTexCoord2sv);
	LOAD_GL_FUNC( PFNGLMULTITEXCOORD3DPROC, glMultiTexCoord3d);
	LOAD_GL_FUNC( PFNGLMULTITEXCOORD3DVPROC, glMultiTexCoord3dv);
	LOAD_GL_FUNC( PFNGLMULTITEXCOORD3FPROC, glMultiTexCoord3f);
	LOAD_GL_FUNC( PFNGLMULTITEXCOORD3FVPROC, glMultiTexCoord3fv);
	LOAD_GL_FUNC( PFNGLMULTITEXCOORD3IPROC, glMultiTexCoord3i);
	LOAD_GL_FUNC( PFNGLMULTITEXCOORD3IVPROC, glMultiTexCoord3iv);
	LOAD_GL_FUNC( PFNGLMULTITEXCOORD3SPROC, glMultiTexCoord3s);
	LOAD_GL_FUNC( PFNGLMULTITEXCOORD3SVPROC, glMultiTexCoord3sv);
	LOAD_GL_FUNC( PFNGLMULTITEXCOORD4DPROC, glMultiTexCoord4d);
	LOAD_GL_FUNC( PFNGLMULTITEXCOORD4DVPROC, glMultiTexCoord4dv);
	LOAD_GL_FUNC( PFNGLMULTITEXCOORD4FPROC, glMultiTexCoord4f);
	LOAD_GL_FUNC( PFNGLMULTITEXCOORD4FVPROC, glMultiTexCoord4fv);
	LOAD_GL_FUNC( PFNGLMULTITEXCOORD4IPROC, glMultiTexCoord4i);
	LOAD_GL_FUNC( PFNGLMULTITEXCOORD4IVPROC, glMultiTexCoord4iv);
	LOAD_GL_FUNC( PFNGLMULTITEXCOORD4SPROC, glMultiTexCoord4s);
	LOAD_GL_FUNC( PFNGLMULTITEXCOORD4SVPROC, glMultiTexCoord4sv);
	LOAD_GL_FUNC( PFNGLLOADTRANSPOSEMATRIXFPROC, glLoadTransposeMatrixf);
	LOAD_GL_FUNC( PFNGLLOADTRANSPOSEMATRIXDPROC, glLoadTransposeMatrixd);
	LOAD_GL_FUNC( PFNGLMULTTRANSPOSEMATRIXFPROC, glMultTransposeMatrixf);
	LOAD_GL_FUNC( PFNGLMULTTRANSPOSEMATRIXDPROC, glMultTransposeMatrixd);

	// OpenGL 1.5
	LOAD_GL_FUNC(PFNGLGENQUERIESPROC, glGenQueries);
	LOAD_GL_FUNC(PFNGLDELETEQUERIESPROC, glDeleteQueries);
	LOAD_GL_FUNC(PFNGLISQUERYPROC, glIsQuery);
	LOAD_GL_FUNC(PFNGLBEGINQUERYPROC, glBeginQuery);
	LOAD_GL_FUNC(PFNGLENDQUERYPROC, glEndQuery);
	LOAD_GL_FUNC(PFNGLGETQUERYIVPROC, glGetQueryiv);
	LOAD_GL_FUNC(PFNGLGETQUERYOBJECTIVPROC, glGetQueryObjectiv);
	LOAD_GL_FUNC(PFNGLGETQUERYOBJECTUIVPROC, glGetQueryObjectuiv);
	LOAD_GL_FUNC(PFNGLBINDBUFFERPROC, glBindBuffer);
	LOAD_GL_FUNC(PFNGLDELETEBUFFERSPROC, glDeleteBuffers);
	LOAD_GL_FUNC(PFNGLGENBUFFERSPROC, glGenBuffers);
	LOAD_GL_FUNC(PFNGLISBUFFERPROC, glIsBuffer);
	LOAD_GL_FUNC(PFNGLBUFFERDATAPROC, glBufferData);
	LOAD_GL_FUNC(PFNGLBUFFERSUBDATAPROC, glBufferSubData);
	LOAD_GL_FUNC(PFNGLGETBUFFERSUBDATAPROC, glGetBufferSubData);
	LOAD_GL_FUNC(PFNGLMAPBUFFERPROC, glMapBuffer);
	LOAD_GL_FUNC(PFNGLUNMAPBUFFERPROC, glUnmapBuffer);
	LOAD_GL_FUNC(PFNGLGETBUFFERPARAMETERIVPROC, glGetBufferParameteriv);
	LOAD_GL_FUNC(PFNGLGETBUFFERPOINTERVPROC, glGetBufferPointerv);
	
	//LogMsg("GL_Load: glActiveTexture=%i glGenBuffers=%i", !!glActiveTexture, !!glGenBuffers);

	g_EXTFramebufferSupport = GL_CheckExtensions("GL_EXT_framebuffer_object");
	if (g_EXTFramebufferSupport)
	{
		LOAD_GL_FUNC(PFNGLISRENDERBUFFEREXTPROC, glIsRenderbufferEXT);
		LOAD_GL_FUNC(PFNGLBINDRENDERBUFFEREXTPROC, glBindRenderbufferEXT);
		LOAD_GL_FUNC(PFNGLDELETERENDERBUFFERSEXTPROC, glDeleteRenderbuffersEXT);
		LOAD_GL_FUNC(PFNGLGENRENDERBUFFERSEXTPROC, glGenRenderbuffersEXT);
		LOAD_GL_FUNC(PFNGLRENDERBUFFERSTORAGEEXTPROC, glRenderbufferStorageEXT);
		LOAD_GL_FUNC(PFNGLGETRENDERBUFFERPARAMETERIVEXTPROC, glGetRenderbufferParameterivEXT);
		LOAD_GL_FUNC(PFNGLISFRAMEBUFFEREXTPROC, glIsFramebufferEXT);
		LOAD_GL_FUNC(PFNGLBINDFRAMEBUFFEREXTPROC, glBindFramebufferEXT);
		LOAD_GL_FUNC(PFNGLDELETEFRAMEBUFFERSEXTPROC, glDeleteFramebuffersEXT);
		LOAD_GL_FUNC(PFNGLGENFRAMEBUFFERSEXTPROC, glGenFramebuffersEXT);
		LOAD_GL_FUNC(PFNGLCHECKFRAMEBUFFERSTATUSEXTPROC, glCheckFramebufferStatusEXT);
		LOAD_GL_FUNC(PFNGLFRAMEBUFFERTEXTURE1DEXTPROC, glFramebufferTexture1DEXT);
		LOAD_GL_FUNC(PFNGLFRAMEBUFFERTEXTURE2DEXTPROC, glFramebufferTexture2DEXT);
		LOAD_GL_FUNC(PFNGLFRAMEBUFFERTEXTURE3DEXTPROC, glFramebufferTexture3DEXT);
		LOAD_GL_FUNC(PFNGLFRAMEBUFFERRENDERBUFFEREXTPROC, glFramebufferRenderbufferEXT);
		LOAD_GL_FUNC(PFNGLGETFRAMEBUFFERATTACHMENTPARAMETERIVEXTPROC, glGetFramebufferAttachmentParameterivEXT);
		LOAD_GL_FUNC(PFNGLGENERATEMIPMAPEXTPROC, glGenerateMipmapEXT);
	}
}

void GL_SwapBuffers(int inverval)
{
}

// Extensions
bool g_EXTFramebufferSupport = false;

// OpenGL 1.3
PFNGLACTIVETEXTUREPROC                  glActiveTexture = NULL;
PFNGLSAMPLECOVERAGEPROC                 glSampleCoverage = NULL;
PFNGLCOMPRESSEDTEXIMAGE3DPROC           glCompressedTexImage3D = NULL;
PFNGLCOMPRESSEDTEXIMAGE2DPROC           glCompressedTexImage2D = NULL;
PFNGLCOMPRESSEDTEXIMAGE1DPROC           glCompressedTexImage1D = NULL;
PFNGLCOMPRESSEDTEXSUBIMAGE3DPROC        glCompressedTexSubImage3D = NULL;
PFNGLCOMPRESSEDTEXSUBIMAGE2DPROC        glCompressedTexSubImage2D = NULL;
PFNGLCOMPRESSEDTEXSUBIMAGE1DPROC        glCompressedTexSubImage1D = NULL;
PFNGLGETCOMPRESSEDTEXIMAGEPROC          glGetCompressedTexImage = NULL;
PFNGLCLIENTACTIVETEXTUREPROC            glClientActiveTexture = NULL;
PFNGLMULTITEXCOORD1DPROC                glMultiTexCoord1d = NULL;
PFNGLMULTITEXCOORD1DVPROC               glMultiTexCoord1dv = NULL;
PFNGLMULTITEXCOORD1FPROC                glMultiTexCoord1f = NULL;
PFNGLMULTITEXCOORD1FVPROC               glMultiTexCoord1fv = NULL;
PFNGLMULTITEXCOORD1IPROC                glMultiTexCoord1i = NULL;
PFNGLMULTITEXCOORD1IVPROC               glMultiTexCoord1iv = NULL;
PFNGLMULTITEXCOORD1SPROC                glMultiTexCoord1s = NULL;
PFNGLMULTITEXCOORD1SVPROC               glMultiTexCoord1sv = NULL;
PFNGLMULTITEXCOORD2DPROC                glMultiTexCoord2d = NULL;
PFNGLMULTITEXCOORD2DVPROC               glMultiTexCoord2dv = NULL;
PFNGLMULTITEXCOORD2FPROC                glMultiTexCoord2f = NULL;
PFNGLMULTITEXCOORD2FVPROC               glMultiTexCoord2fv = NULL;
PFNGLMULTITEXCOORD2IPROC                glMultiTexCoord2i = NULL;
PFNGLMULTITEXCOORD2IVPROC               glMultiTexCoord2iv = NULL;
PFNGLMULTITEXCOORD2SPROC                glMultiTexCoord2s = NULL;
PFNGLMULTITEXCOORD2SVPROC               glMultiTexCoord2sv = NULL;
PFNGLMULTITEXCOORD3DPROC                glMultiTexCoord3d = NULL;
PFNGLMULTITEXCOORD3DVPROC               glMultiTexCoord3dv = NULL;
PFNGLMULTITEXCOORD3FPROC                glMultiTexCoord3f = NULL;
PFNGLMULTITEXCOORD3FVPROC               glMultiTexCoord3fv = NULL;
PFNGLMULTITEXCOORD3IPROC                glMultiTexCoord3i = NULL;
PFNGLMULTITEXCOORD3IVPROC               glMultiTexCoord3iv = NULL;
PFNGLMULTITEXCOORD3SPROC                glMultiTexCoord3s = NULL;
PFNGLMULTITEXCOORD3SVPROC               glMultiTexCoord3sv = NULL;
PFNGLMULTITEXCOORD4DPROC                glMultiTexCoord4d = NULL;
PFNGLMULTITEXCOORD4DVPROC               glMultiTexCoord4dv = NULL;
PFNGLMULTITEXCOORD4FPROC                glMultiTexCoord4f = NULL;
PFNGLMULTITEXCOORD4FVPROC               glMultiTexCoord4fv = NULL;
PFNGLMULTITEXCOORD4IPROC                glMultiTexCoord4i = NULL;
PFNGLMULTITEXCOORD4IVPROC               glMultiTexCoord4iv = NULL;
PFNGLMULTITEXCOORD4SPROC                glMultiTexCoord4s = NULL;
PFNGLMULTITEXCOORD4SVPROC               glMultiTexCoord4sv = NULL;
PFNGLLOADTRANSPOSEMATRIXFPROC           glLoadTransposeMatrixf = NULL;
PFNGLLOADTRANSPOSEMATRIXDPROC           glLoadTransposeMatrixd = NULL;
PFNGLMULTTRANSPOSEMATRIXFPROC           glMultTransposeMatrixf = NULL;
PFNGLMULTTRANSPOSEMATRIXDPROC           glMultTransposeMatrixd = NULL;

// OpenGL 1.5
PFNGLGENQUERIESPROC glGenQueries = NULL;
PFNGLDELETEQUERIESPROC glDeleteQueries = NULL;
PFNGLISQUERYPROC glIsQuery = NULL;
PFNGLBEGINQUERYPROC glBeginQuery = NULL;
PFNGLENDQUERYPROC glEndQuery = NULL;
PFNGLGETQUERYIVPROC glGetQueryiv = NULL;
PFNGLGETQUERYOBJECTIVPROC glGetQueryObjectiv = NULL;
PFNGLGETQUERYOBJECTUIVPROC glGetQueryObjectuiv = NULL;
PFNGLBINDBUFFERPROC glBindBuffer = NULL;
PFNGLDELETEBUFFERSPROC glDeleteBuffers = NULL;
PFNGLGENBUFFERSPROC glGenBuffers = NULL;
PFNGLISBUFFERPROC glIsBuffer = NULL;
PFNGLBUFFERDATAPROC glBufferData = NULL;
PFNGLBUFFERSUBDATAPROC glBufferSubData = NULL;
PFNGLGETBUFFERSUBDATAPROC glGetBufferSubData = NULL;
PFNGLMAPBUFFERPROC glMapBuffer = NULL;
PFNGLUNMAPBUFFERPROC glUnmapBuffer = NULL;
PFNGLGETBUFFERPARAMETERIVPROC glGetBufferParameteriv = NULL;
PFNGLGETBUFFERPOINTERVPROC glGetBufferPointerv = NULL;

// GL_EXT_framebuffer_object
PFNGLISRENDERBUFFEREXTPROC                         	glIsRenderbufferEXT = NULL;
PFNGLBINDRENDERBUFFEREXTPROC                       	glBindRenderbufferEXT = NULL;
PFNGLDELETERENDERBUFFERSEXTPROC                    	glDeleteRenderbuffersEXT = NULL;
PFNGLGENRENDERBUFFERSEXTPROC                       	glGenRenderbuffersEXT = NULL;
PFNGLRENDERBUFFERSTORAGEEXTPROC                    	glRenderbufferStorageEXT = NULL;
PFNGLGETRENDERBUFFERPARAMETERIVEXTPROC             	glGetRenderbufferParameterivEXT = NULL;
PFNGLISFRAMEBUFFEREXTPROC                          	glIsFramebufferEXT = NULL;
PFNGLBINDFRAMEBUFFEREXTPROC                        	glBindFramebufferEXT = NULL;
PFNGLDELETEFRAMEBUFFERSEXTPROC                     	glDeleteFramebuffersEXT = NULL;
PFNGLGENFRAMEBUFFERSEXTPROC                        	glGenFramebuffersEXT = NULL;
PFNGLCHECKFRAMEBUFFERSTATUSEXTPROC                 	glCheckFramebufferStatusEXT = NULL;
PFNGLFRAMEBUFFERTEXTURE1DEXTPROC                   	glFramebufferTexture1DEXT = NULL;
PFNGLFRAMEBUFFERTEXTURE2DEXTPROC                   	glFramebufferTexture2DEXT = NULL;
PFNGLFRAMEBUFFERTEXTURE3DEXTPROC                   	glFramebufferTexture3DEXT = NULL;
PFNGLFRAMEBUFFERRENDERBUFFEREXTPROC                	glFramebufferRenderbufferEXT = NULL;
PFNGLGETFRAMEBUFFERATTACHMENTPARAMETERIVEXTPROC    	glGetFramebufferAttachmentParameterivEXT = NULL;
PFNGLGENERATEMIPMAPEXTPROC                         	glGenerateMipmapEXT = NULL;